PAD is a widely prevalent condition, affecting 15% of the Medicare population. Endovascular procedures, such as angioplasty/stent, are the usual initial surgical procedure; close to a million were performed last year. Unfortunately, many of these procedures fail within a few years. In fact, less than half of such procedures are successful at two years. However, some endovascular repairs endure for many years. This suggests that with improved technique it may be possible to extend the longevity of most, rather than some, of these procedures, with significant benefit to the millions of patients and health-care system. It is a well-accepted principle of vascular surgery that good blood flow keeps repaired vessels healthy, and poor flow leads to early failure. Present endovascular procedures employ a subjective method of assessing the post-procedure blood flow. We propose using a newly developed ultrasound system specifically designed to be used during endovascular procedures to measure the changes in blood flow. Our hypothesis is that by measuring the blood flow during endovascular procedures and following the outcome for these patients, we can develop criteria for the flow needed to achieve long-term repair. Measuring flow with the new system during the procedure can then guide treatment, so that long-lasting repair by endovascular procedures becomes the norm rather than the exception. In Phase I, we propose establishing the new instrument's accuracy and reliability for measuring blood flow before, during, and after the endovascular intervention. Milestones for Phase I include: 1) showing that for a consecutive run of patients the instrument's results are consistent with other measures of flow, such as duplex Doppler and ABI; 2) demonstrating that the new instrument can be used easily in the endovascular procedure room; and 3) confirming that the instrument's cost is low enough to be widely used. If Phase I is successful, in Phase II the instrument will be used to measure changes of flow produced during endovascular procedures for a large cohort of patients. By correlating the outcomes of these procedures with the flows measured during the procedure, criteria for a successful procedure can be determined. Treatment will then be guided by flow measurements, and endovascular treatment can become more successful, a boon to patients and the health-care system.